1. Field of the Invention
The present invention relates to materials for the manufacture of nonwoven wipers particularly suited for industrial uses. Industrial wipers are currently either reusable cloth, in the form of manufactured wipers or rags, or nonwoven fabric material intended for disposable or limited use applications. The nonwoven material segment of this market has grown due to the economy of such products as well as the ability to tailor the wipers for specific applications. For example, nonwoven wipers are available having absorbency properties particularly suited for oil wiping, for food services wiping, and for wiping of high technology electronic parts. Such nonwoven wiper materials may be manufactured by a number of known processes including wet forming, air forming, and extrusion of thermoplastic fibers. The present invention is related to improvements in nonwoven wipers formed using a meltblowing process to produce microfibers and resulting wipers having utility and diverse applications, particularly where clean wiping properties are essential.
2. Description of the Prior Art
Meltblown nonwoven microfiber wiper materials are known and have been described in a number of U.S. Patents, including 4,328,279 to Meitner and Englebert dated May 4, 1982, U.S. Pat. Nos. 4,298,649 to Meitner dated Nov. 3, 1981, and 4,307,143 to Meitner dated Dec. 22, 1981. The preparation of thermoplastic microfiber webs is also known and described, for example, in Went, Industrial and Engineering Chemistry, Vol. 48, No. 8 (1956) pages 1342 through 1346, as well as in U.S. Pat. Nos. 3,978,185 to Buntin, et al. dated Aug. 31, 1976, 3,795,571 to Prentice dated Mar. 5, 1975, and 3,811,957 to Buntin dated May 21, 1974, for example. These processes generally involve forming a low viscosity thermoplastic polymer melt and extruding filaments into converging air streams which draw the filaments to fine diameters on the average of up to about 10 microns which are collected to form a nonwoven web. The addition of pulp to the air stream to incorporate pulp fibers into the meltblown fiber web is also known and described, for example, in U.S. Pat. No. 4,100,324 to Anderson, Sokolowski, and Ostermeier dated July 11, 1978. The incorporation of staple thermoplastic fibers into meltblown webs is further known and described, for example, in British Published Patent application No. 2,031,039A to Jacques dated Apr. 16, 1980, as well as earlier U.S. Pat. Nos. such as 2,988,469 to Watson dated Jun. 13, 1961 and 3,016,599 to Perry dated Jan. 16, 1962.
While wipers produced in accordance with the disclosures of these patents have, in some cases, achieved good acceptance for a number of wiping applications, it remains desired to produce a nonwoven wiper having extremely good clean wiping properties, i.e., the ability to wipe quickly leaving little or no streaks or residue. In addition, the pulp additive materials tend to be weak and linty and, therefore, unsuitable for many wiping applications. Further, it is desired to produce such a wiper at a cost consistent with disposability and having strength properties for rigorous wiping applications. The wipers of the present invention attain to a high degree these desired attributes and yet further improve the economies of the manufacture of nonwoven disposable wipers.